1. Field of the Invention
The present invention relates to a construction machine provided with an air intake structure configured to draw an external air into an engine room and to guide the external air to a heat exchanger for cooling the heat exchanger.
2. Description of the Background Art
The background art is described taking an example of an excavator (shovel).
In an excavator, an engine room is disposed at a rear portion of an upper slewing body. An engine, a hydraulic pump, a cooling fan, and a heat exchanger such as a radiator and an oil cooler are disposed side by side in the engine room in the width direction of the upper slewing body. The excavator is constructed in such a manner that an air for cooling drawn from the exterior of the engine room and passed through the heat exchanger by rotation of the cooling fan.
In the conventional excavator, normally, an air intake port for drawing an external air into an engine room is formed in a side surface of the engine room in the width direction of the upper slewing body, or in a top surface of the engine room. In such a construction, intolerable degree of noise from the engine and in the vicinity of the engine, in other words, noise (hereinafter, generically called as “engine periphery noise”) such as engine sound, pump sound, and fan sound may leak through the air intake port.
A technology has been proposed to solve the above drawback, as disclosed in Japanese Unexamined Patent Publication No. Hei 4-55527. The publication discloses a configuration that an air intake duct is formed into a curved shape extending from a front surface of a portion of a construction machine close to one widthwise end of the construction machine to an air intake surface of a heat exchanger. The forming the air intake duct into the curved shape increases the length of an air intake passage, whereby a noise reduction effect in the passage is enhanced. As a result, noise leakage through an air intake port is reduced.
In the above well-known technology, however, the entirety of the air intake duct is configured to have substantially the same height as the height of a main source of noise such as sounds of an engine and a cooling fan, and in such a state that engine periphery noise directly enters the duct. As a result, the absolute volume of engine periphery noise entering the air intake passage of the air intake duct increases. Further, in the above well-known technology, although the air intake duct is curved along the slewing direction of the upper slewing body, the air intake duct is not provided with a largely bent portion capable of blocking propagation of noise, which is believed to provide an enhanced noise reduction effect. Consequently, the noise reduction effect in the air intake duct is lowered. In view of these drawbacks, engine periphery noise which may leak to the exterior through the air intake port of the air intake duct increases. Thus, the noise reduction effect is low in the above well-known technology.